Method and system for feeding and transporting documents

ABSTRACT

A system and method for feeding and transporting documents are provided. The system includes a feeder stage including a hopper, a feeder and a separator. The hopper includes a hopper wall extending toward the feeder with a waterfall step along the hopper wall and with the stack of documents engaging the hopper wall including the waterfall step to form a pocket area over a limited distance extending from the waterfall step along the hopper wall toward the feeder. A photo edge detector located in the pocket area faces the stack of documents such that when a feeding document trailing edge passes the waterfall step, the trailing edge is detected by the photo edge detector while in the pocket area. The system further includes a transport stage downstream of the feeder stage for receiving the fed documents.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods for feeding andtransporting documents and to detecting a document trailing edge.

2. Background Art

A typical system for feeding and transporting documents includes afeeder and a separator in the document feeding portion of the system,and a series of roller pairs or belts in the document transportingportion of the system. In the feeding portion of the system, the feederacts with the separator to feed documents singly, in order, from astack. In the transporting portion of the system, the roller pairsand/or belts convey the documents, one at a time, past other processingdevices such as readers, printers, and sorters that perform operationson the documents. The feeder is typically a feed wheel, but may takeother forms. The separator may be a wheel, but also may take other formssuch as a belt. Further, the components in the transporting portion ofthe system may take a variety of forms. The systems also include acomponent in the document feeding portion of the system that nudgesdocuments into the nip between the feeder and the separator. A suitablenudger may be a nudger wheel, but may take other forms. An existingdocument feeder is shown in U.S. Pat. No. 6,199,854. That patentdescribes a document feeder with a variable speed separator.

In existing systems for feeding and transporting documents, operationsthat depend on the position of the document are generally performed inthe transport stage, or transporting portion of the system. For example,U.S. Pat. No. 5,848,784 describes a document separation apparatus. Thatpatent describes the downstream acceleration/deceleration of documentswith pinch rollers to adjust document spacing. U.S. Pat. Nos. 5,419,546;5,437,375; 5,439,506; 5,509,648; 5,671,919; and 5,908,191 describeexamples of other document operations.

Workers will understand the importance of detecting the leading andtrailing edges of documents, and the gaps between them, as they passthrough the feeding system and the transport system beyond. Manyoperations to be performed upon the documents (for example, printing,reading, imaging and so forth) are required to be performed at specificlocations along the length of the document, and so it is very importantfor the system to be able to detect when the leading or trailing edge ofa document appears at a specific point. From this data, the system canextrapolate its necessary understanding of where the document is, howfast it is traveling, and when and where specific operations should beperformed upon it.

Similarly, it is just as important for the system to understand thelengths and locations of gaps between documents as it is for it tounderstand the lengths and locations of the documents themselves. Itwill be understood that document processing systems seek to produce thehighest possible throughput rates, and therefore, workers seek tominimize gaps between successive documents. At a given transport speed,a gap is a unit of time in the operation of the system which is notoccupied by a document, and is therefore lost to productive processing.At the same time, systems often require a discrete and controlled timeinterval between documents, for example, to transmit data gathered fromthe previous document, or to reset mechanisms after processing theprevious document, and the optimum gap is usually dependent upon thelength of the previous document. The longer the previous document(generally speaking) the longer the gap required after it before thesystem can be ready to commence processing the next document.

Workers therefore always seek to reduce the gaps between documents tothe smallest possible consistent with all system functions, and forsystem functions, gaps are most usually dealt with as time measurementsrather than measurements of physical distance. In order to best measureand manage both document lengths and the gaps between them for theoptimum throughput, workers will understand that it is advantageous tobe able to detect both leading and trailing edges of documents as earlyin their processing as possible, and preferably, during the feedingprocess, before any other processes are to be performed upon them.

Ideally, such a system would measure the position of the edges of thedocument in the feed hopper even before it is fed. However, documentscan vary widely in overall length. For example, if we consider ahigh-speed document processing machine such as the Unisys NDP2000, thespecified range of document length is 4.25″-9.25″, or a range greaterthan 100% between shortest and longest. There is a need to detecttrailing edges of unequal length documents, while in motion, beforedocuments leave the feeder area to sense for overlapping and aid incontrolling spacing between documents. To meet this need a detectorcapable of detecting over a wide possible range of document trailingedge positions would be required. It is found that a single detector, ata suitable fixed location in the feed hopper consistent with theshortest possible document length, serves the desired function.

In order to perform operations on documents that depend on documentposition, leading and/or trailing document edges are detected dependingon the operation to be performed. A known device for detecting documentedges is the photo edge detector. U.S. Pat. No. 5,848,784 describes theuse of an edge detector. The edge detector is suitable for someapplications, but may be sensitive to, for example, printing on thedocuments and/or document thickness and/or opacity. There is a need toovercome the optical sensor's inability to differentiate between thetrailing edge of documents and printing, fold lines, holes or otherdocument characteristics that look like a document edge.

Workers will understand that photo edge detectors can be and are used todetect both leading and trailing edges of documents, but they can onlyfunction upon individual documents, for example when traveling singly ina document track. Since they rely for their function upon theinterruption of a beam of light, traditional photo edge detectorapplications are unsuitable for use in a feed hopper which contains manydocuments in a stack because the document trailing edge may be difficultto identify particularly against the document stack and other documentcharacteristics that look like a document edge. Such sensors intraditional applications have been used to detect leading edges ofdocuments as they leave the stack in the feed hopper, but cannot be usedto detect trailing edges until the trailing edge has entirely separatedfrom the stack of documents behind it in the feed hopper.

For the foregoing reasons, there is a need for an improved system andmethod for feeding and transporting documents that detect a documenttrailing edge at a known location with a photo edge detector while it isstill within the feed hopper.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide animproved system and method for feeding and transporting documents thatdetect, based on a photo edge detector, a document trailing edge at aknown location within a feed hopper, while the document whose trailingedge is to be detected is still in the process of being fed from thestack of documents behind it.

In carrying out the above object, a system for feeding and transportingdocuments is provided. Each document has a leading edge and a trailingedge. The system comprises a feeder stage, a photo edge detector and atransport stage. The feeder stage includes a hopper, a feeder and aseparator. The feeder acts with the separator to feed documents singly,in order, from a stack of documents in the hopper. The hopper includes ahopper wall extending toward the feeder with a waterfall step along thehopper wall and with the stack of documents engaging the hopper wallincluding the waterfall step to form a pocket area. The pocket area isformed over a limited distance extending from the waterfall step alongthe hopper wall toward the feeder. The photo edge detector is located inthe pocket area and faces the stack of documents such that a feedingdocument slides between the stack of documents and the hopper wall. Thefeeding document trailing edge passes the waterfall step and is detectedby the photo edge detector while in the pocket area. The transport stageis downstream of the feeder stage for receiving the fed documents.

By adding a waterfall step in the hopper wall at a specific height andan optical sensor at a specific distance from this step, a void orpocket area is created where documents in the stack are outside of theoptical sensor's viewing range. As the trailing edge of the fed documentclears the step, it snaps down into viewing range of the sensorsignaling the trailing edge without adding unwanted drag on thedocument. Advantageously, this technique does not require additionalmoving mechanical parts or opposing forces on the documents as they movetoward the feeder in the hopper. The photo edge detector may suitably beimplemented as a single optical sensor, however, an array of photo edgedetectors could alternatively be located in the pocket area. The arraywould provide more information for determining the feeding documenttrailing edge position and would accommodate documents of varyingthicknesses that result in pocket areas of varying sizes.

At a more detailed level, the present invention comprehends controllogic in communication with the photo edge detector or detectors fordetermining the feeding document trailing edge position based on thephoto edge detector or detectors, and a control device. The controldevice performs a document processing function in response to directionfrom the control logic.

Further, in carrying out the present invention, a method for feeding andtransporting documents is provided. Each document has a leading edge anda trailing edge. The method comprises providing a feeder stage,providing a photo edge detector, and providing a transport stage. Thefeeder stage includes a hopper, a feeder and a separator. The feederacts with the separator to feed documents singly, in order, from a stackof documents in the hopper. The hopper includes a hopper wall extendingtoward the feeder with a waterfall step along the hopper wall and withthe stack of documents engaging the hopper wall including the waterfallstep. This forms a pocket area over a limited distance extending fromthe waterfall step along the hopper wall toward the feeder. The photoedge detector is located in the pocket area and faces the stackeddocuments. A feeding document slides between the stack of documents andthe hopper wall with the feeding document trailing edge passing thewaterfall step and being detected by the photo edge detector while inpocket area. The transport stage is downstream of the feeder stage forreceiving the fed documents.

At a more detailed level, the method may alternatively utilize an arrayof photo edge detectors located in the pocket area and includes thesteps of determining the feeding document trailing edge position basedon the photo edge detector(s) and performing a document processingfunction in response to the feeding document trailing edge position.

The advantages associated with embodiments of the present invention arenumerous. For example, embodiments of the present invention detect adocument trailing edge at a known location by sensing the documenttrailing edge with an optical sensor. Embodiments of the presentinvention are suitable for use in a feed hopper. Detecting the trailingedge position while the document is still in the feeder allowsoperations to be performed on the document, as well as other operationsto be performed while the document is still in the feeder. In addition,knowing the trailing edge position allows a system to know when toperform operations on subsequent documents. Many document processingproducts could benefit from embodiments of the present invention. Forexample, copiers, fax machines, sheet feeders for computer printers,automatic teller machines, and document image scanners are just a fewexamples of products that could benefit from embodiments of the presentinvention.

The above objects and other objects, features, and advantages of thepresent invention are readily apparent from the following detailingdescription of the preferred embodiment when taken in connection withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary system for feeding and transportingdocuments in accordance with the present invention; and

FIG. 2 is a block diagram illustrating a method of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a system for feeding and transporting documents. Thesystem includes a feeder stage 10 and a transport stage 12. Feeder stage10 includes a feeder 14 and a separator 16. Transport stage 12 isdownstream of feeder stage 10, with arrow 18 pointing in the downstreamdirection. A document leading edge LE is the more downstream edge whilethe trailing edge TE is the more upstream edge. Feeder stage 10 furtherincludes hopper 20. Hopper 20 includes a hopper wall 21 extending towardfeeder 14 with a waterfall step 22 along hopper wall 21. A stack 32 ofdocuments engages hopper wall 21 including waterfall step 22 to form apocket area over a limited distance extending from waterfall step 22along hopper wall 21 toward feeder 14. A photo edge detector 24 isdirected toward a fixed location upstream of feeder 14 in the pocketarea and faces stack 32 of documents. A feeding document slides betweenstack 32 of documents and hopper wall 21 with the feeding documenttrailing edge TE passing waterfall step 22 and being detected by photoedge detector 24 while in the pocket area. In FIG. 1, motion of thetrailing edge TE is shown in phantom.

By adding waterfall step 22 in hopper wall 21 at a specific height andphoto edge detector or optical sensor 24 at a specific distance fromstep 22, the pocket area is created where documents in stack 32 areoutside of the sensor viewing range of photo edge detector 24. As thefeeding document trailing edge TE clears step 22, it snaps down intoviewing range of photo edge detector 24 signaling the trailing edgewithout adding unwanted drag on the documents, requiring movingmechanical parts, or requiring opposing forces on the documents as theymove toward feeder 14 from hopper 20. This arrangement overcomes thetypical optical sensor inability to differentiate between the trailingedge of documents and printing, fold lines, holes or other documentcharacteristics that look like a document edge.

Control logic 26 is configured to detect a signal from sensor 24indicating when a document trailing edge TE passes. Control logic 26also provides an output signal, which is provided to a control device40. Control logic 26 may direct control device 40 to perform documentprocessing functions based on knowledge of the trailing edge position.Further, control logic 26 may perform system diagnostics based onreceived signals.

Document stack 32 is shown adjacent to separator 16 and includes firstdocument 30 among other documents in stack 32, with the trailing edge offirst document 30 being in the pocket area. The components shown in FIG.1 are exemplary, and alternative arrangements are possible as known tothose skilled in the art. For example, the feeder is shown as a feedwheel 14, but may take other forms. The separator is shown as aseparator wheel 16, but also may take other forms such as a belt. Asshown, feed wheel 14 rotates clockwise, driven by its own motor (notshown), and separator or retarder wheel 16 is fixed or runs slowlyrelative to the speed of the feed wheel 14. Further, the components intransporting portion 12 may take a variety of forms as known to thoseskilled in the art, but for convenience of understanding are shown as anaccelerator idler wheel 36 and an accelerator drive wheel 38 thatrotates clockwise. The system may also include a suitable nudging devicesuch as nudger wheel 34.

With continuing reference to FIG. 1, feed wheel 14, separator 16, andnudger 34 are typical elements for feeding documents singly from adocument stack. Downstream accelerator wheel pair 36, 38 accepts thedocument from feed wheel 14 and separator 16. The accelerator drivewheel 38 may or may not be driven by the same motor that drives feedwheel 14 and may run at the same or higher peripheral speed than feedwheel 14. Further, feed wheel 14 may or may not have a greater grip onthe document than the accelerator wheel pair, depending upon theapplication. Feed wheel 14 may or may not have attached to it a deviceto indicate relative feed wheel position.

The system shown in FIG. 1 detects, or registers the presence orarrival, of trailing edge TE of document 30 at a known location in thepocket area based upon detection from photo edge detector 24. Detectingthe trailing edge of a moving document while still in the feed hopperhas many advantages. For example, using any appropriate technique knownin the art, the total length of the document may be determined, earlierin the feeding cycle, thus allowing various other document processingfunctions to be performed upon the documents sooner, faster, and/or atlower cost.

It is appreciated that characteristics of the documents in documentstack 32 affect the size of the pocket area. Detector 24 is placed at aspecific distance from waterfall step 22 so as to be located in thepocket area to detect the passing of the trailing edge. Some embodimentsof the present invention may utilize an array of photo edge detectors.As shown in FIG. 1, photo edge detector 42 is optional and also providesinformation to control logic 26.

Further, it is appreciated by those skilled in the art that embodimentsof the present invention may be applied in multiple locations upon thesame item. For example, the system could be applied at various points inthe height of the item being fed to obtain a reliable signal of thetrailing edge that is not affected by the presence of holes or tears inthe item. This is an addition to the possibility of using an array ofphoto edge detectors to get sequential signals of the trailing edge ofthe item which could be used to calculate the speed of the item or toaccommodate for varying documents that create different pocket sizes.

FIG. 2 is a block diagram illustrating a method of the presentinvention. At block 50, a feeder stage including a hopper with awaterfall step to form a pocket area is provided. At block 52, a photoedge detector is provided in the pocket area. At block 54, a transportstage is provided. At block 56, document trailing edge position isdetermined based on signals from the photo edge detector. At block 58, adocument processing function is performed in response to the documenttrailing edge position.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

What is claimed is:
 1. A system for feeding and transporting documents,each document having a leading edge and a trailing edge, the systemcomprising: a feeder stage including a hopper, a feeder and a separatorwherein the feeder acts with the separator to feed documents singly, inorder, from a stack of documents in the hopper, the hopper including ahopper wall extending toward the feeder with a waterfall step along thehopper wall and with the stack of documents engaging the hopper wallincluding the waterfall step to form a pocket area over a limiteddistance extending from the waterfall step along the hopper wall towardthe feeder; a photo edge detector located in the pocket area and facingthe stack of documents such that a feeding document slides between thestack of documents and the hopper wall with the feeding documenttrailing edge passing the waterfall step and being detected by the photoedge detector while in the pocket area; and a transport stage downstreamof the feeder stage for receiving the fed documents.
 2. The system ofclaim 1 further comprising: an array of photo edge detectors located inthe pocket area.
 3. The system of claim 1 further comprising: controllogic in communication with the photo edge detector for determining thefeeding document trailing edge position based on the photo edgedetector; and a control device for performing a document processingfunction in response to direction from the control logic.
 4. A methodfor feeding and transporting documents, each document having a leadingedge and a trailing edge, the method comprising: providing a feederstage including a hopper, a feeder and a separator wherein the feederacts with the separator to feed documents singly, in order, from a stackof documents in the hopper, the hopper including a hopper wall extendingtoward the feeder with a waterfall step along the hopper wall and withthe stack of documents engaging the hopper wall including the waterfallstep to form a pocket area over a limited distance extending from thewaterfall step along the hopper wall toward the feeder; providing aphoto edge detector located in the pocket area and facing the stack ofdocuments such that a feeding document slides between the stack ofdocuments and the hopper wall with the feeding document trailing edgepassing the waterfall step and being detected by the photo edge detectorwhile in the pocket area; and providing a transport stage downstream ofthe feeder stage for receiving the fed documents.
 5. The method of claim1 further comprising: providing an array of photo edge detectors locatedin the pocket area.
 6. The method of claim 1 further comprising:determining the feeding document trailing edge position based on thephoto edge detector; and performing a document processing function inresponse to the feeding document trailing edge position.